Many on-line, handwriting recognition systems employ curve matching methods to match an unknown character against prototype, or template, characters. Examples of such systems are described in the following articles: W. Doster and R. Oed, "Word processing with on-line script recognition," IEEE Micro., vol. 4, pp. 36-43, October 1984; K. Ikeda, T. Yamamura, Y. Mitamura, S. Fujiwara, Y. Tominaga, and T. Kiyono, "On-line recognition of handwritten characters utilizing positional and stroke vector sequences," Proc. 4th Int. Jt. Conf. Pattern Recognition, pp. 813-815, November 1978; C.C. Tappert, "Adaptive on-line handwriting recognition," Proc. 7th Int. Conf. Pattern Recognition, pp. 1004-1007, 1984; C.C. Tappert, "Speed, accuracy, flexibility trade-offs in on-line character recognition," IBM Research Report RC13228, October 1987; and T. Wakahara and M. Umeda, "Stroke-number and stroke-order free on-line character recognition by selective stroke linkage method," Proc. 4th ICTP, pp. 157-162, 1983. In general, the recognition accuracy of such prototype-based handwriting recognition systems is a function of the quality of the prototypes.
One problem encountered in on-line handwriting recognition is the discrimination of similarly-shaped handwritten characters, such as A-H, h-k, g-y, etc. In that known curve matching methods weigh all portions of the curves of characters equally, non-essential portions may cause errors. In particular, with curve matching methods an unimportant feature or portion of the character, such as the shape of the descender or tail of "g" and "y", may cause recognition errors.
The following U.S. and Japanese Patents all teach various aspects of handwriting recognition systems.
U.S. Pat. No 4,561,105, issued Dec. 24, 1985, entitled "Complex Pattern Recognition Method and System" to Crane et al. describes an on-line character recognition system that uses template or model strokes (col. 3, lines 1-52).
U.S. Pat. No. 4,573,196, issued Feb. 25, 1986, entitled "Confusion Grouping of Strokes in Pattern Recognition Method and System" to Crane et al. also describes an on-line character recognition system that uses template or model strokes and which further provides a distance metric to categorize a stroke as a member of a "confusion group".
U.S. Pat. No. 4,718,102, issued Jan. 5, 1988, entitled "Process and Apparatus Involving Pattern Recognition" to Crane et al. describes a handwritten character recognition system having disambiguation routines to differentiate members of confusion sets of characters (col. 4).
U.S. Pat. No. 4,754,489, issued Jun. 28, 1988, entitled "Means for Resolving Ambiguities in Text Based Upon Character Context" to Bokser describes a context algorithm that assigns a probability value to each member of a set of character strings in order to determine which character string in a set has a highest probability.
Commonly assigned U.S. Pat. No. 4,731,857, issued Mar. 15, 1988, entitled "Recognition System for Run-on Handwritten Characters" to C.C. Tappert describes a segmentation method for run-on handwritten characters that considers all stroke ends as possible character segmentation points.
U.S. Pat. No. 4,491,965, issued Jan. 1, 1985, entitled "Character Recognition Apparatus" to Yoshimura describes character recognition apparatus that provides normalized character patterns to a recognizing section which compares the normalized pattern with entries in a dictionary.
U.S. Pat. No. 4,654,873, issued Mar. 31, 1987, entitled "System and Method for Segmentation and Recognition of Patterns" to Fujisawa et al. describes a character recognition system for use in an optical character reader in which predetermined unit patterns are extracted from a two-dimensional image pattern. If an ambiguity exists in segmentation of the unit patterns, a number of hypothetical unit patterns are provided for the recognition unit for selecting one of the hypothetical unit patterns.
Japanese Patent No. 62-24382 entitled "Method for Recognizing Handwritten Character" describes, in the abstract, a method for recognizing handwritten characters in which input strokes are compared with reference strokes stored in a template memory.
Japanese Patent No. 61-68678 entitled "Optical Input Device of Drawing" describes an optical drawing input device where a symbol on a template is traced and compared to a registered symbol.
What is not taught by this prior art, and what is thus an object of the invention to provide, is method and apparatus for improving or optimizing a set of character prototypes, especially prototypes of character pairs that are known to be readily confusable one with the other.
A further object of the invention is to provide a method, and a means for accomplishing the method, that processes a pair of readily confusable character prototypes so as to emphasize the differences between the characters while also deemphasizing the similarities between the characters.